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<li class="level1"><a href="#properties">属性</a></li>
<li class="level1"><a href="#details">详细信息</a></li>
<li class="level2"><a href="#example-usage">示例用法</a></li>
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<h1 class="title">QML的HistoryState类型 </h1>
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<!-- $$$HistoryState-brief -->
<p><a href="qml-qtqml-statemachine-historystate.html">HistoryState</a> 型提供了返回到先前活动子状态的方法。<a href="#details">更多…</a></p>
<!-- @@@HistoryState -->
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> 导入语句:</td><td class="memItemRight bottomAlign"> import QtQml.StateMachine 1.12</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Since:</td><td class="memItemRight bottomAlign">  Qt 5.4</td></tr><tr><td class="memItemLeft rightAlign topAlign">继承自：</td><td class="memItemRight bottomAlign"> <p><a href="qml-qtqml-statemachine-qabstractstate.html">QAbstractState</a></p>
</td></tr></table></div><ul>
<li><a href="qml-qtqml-statemachine-historystate-members.html">所有成员的列表，包括继承的成员</a></li>
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<a name="properties"></a>
<h2 id="properties">属性</h2>
<ul>
<li class="fn"><b><b><a href="qml-qtqml-statemachine-historystate.html#defaultState-prop">defaultState</a></b></b> : QAbstractState</li>
<li class="fn"><b><b><a href="qml-qtqml-statemachine-historystate.html#historyType-prop">historyType</a></b></b> : enumeration</li>
</ul>
<!-- $$$HistoryState-description -->
<a name="details"></a>
<h2 id="details">详细信息</h2>
<p>历史状态是一个伪状态，表示父状态上次退出父状态时所在的子状态。以历史状态为目标的转换实际上是到父状态的其他子状态之一的转换。<a href="qml-qtqml-statemachine-historystate.html">HistoryState</a>是<a href="qmlstatemachine.html">声明性状态机框架</a>的一部分。</p>
<p>使用<a href="qml-qtqml-statemachine-historystate.html#defaultState-prop">defaultState</a> 属性设置如果从未输入父状态，则应该输入的状态。</p>
<a name="example-usage"></a>
<h2 id="example-usage">示例用法</h2>
<pre class="qml">

  import QtQuick 2.0
  import QtQml.StateMachine 1.0 as DSM

  <span class="type"><a href="../qtquick/qml-qtquick-rectangle.html">Rectangle</a></span> {
      <span class="type"><a href="../qtquickcontrols/qml-qtquick-controls2-button.html">Button</a></span> {
          <span class="name">anchors</span>.fill: <span class="name">parent</span>
          <span class="name">id</span>: <span class="name">button</span>
          <span class="name">text</span>: <span class="string">&quot;Press me&quot;</span>
          <span class="type">DSM</span>.StateMachine {
              <span class="name">id</span>: <span class="name">stateMachine</span>
              <span class="name">initialState</span>: <span class="name">parentState</span>
              <span class="name">running</span>: <span class="number">true</span>
              <span class="type">DSM</span>.State {
                  <span class="name">id</span>: <span class="name">parentState</span>
                  <span class="name">initialState</span>: <span class="name">child2</span>
                  <span class="name">onEntered</span>: <span class="name">console</span>.<span class="name">log</span>(<span class="string">&quot;parentState entered&quot;</span>)
                  <span class="name">onExited</span>: <span class="name">console</span>.<span class="name">log</span>(<span class="string">&quot;parentState exited&quot;</span>)
                  <span class="type">DSM</span>.State {
                      <span class="name">id</span>: <span class="name">child1</span>
                      <span class="name">onEntered</span>: <span class="name">console</span>.<span class="name">log</span>(<span class="string">&quot;child1 entered&quot;</span>)
                      <span class="name">onExited</span>: <span class="name">console</span>.<span class="name">log</span>(<span class="string">&quot;child1 exited&quot;</span>)
                  }
                  <span class="type">DSM</span>.State {
                      <span class="name">id</span>: <span class="name">child2</span>
                      <span class="name">onEntered</span>: <span class="name">console</span>.<span class="name">log</span>(<span class="string">&quot;child2 entered&quot;</span>)
                      <span class="name">onExited</span>: <span class="name">console</span>.<span class="name">log</span>(<span class="string">&quot;child2 exited&quot;</span>)
                  }
                  <span class="type">DSM</span>.HistoryState {
                      <span class="name">id</span>: <span class="name">historyState</span>
                      <span class="name">defaultState</span>: <span class="name">child1</span>
                  }
                  <span class="type">DSM</span>.SignalTransition {
                      <span class="name">targetState</span>: <span class="name">historyState</span>

                      <span class="comment">// Clicking the button will cause the state machine to enter the child state</span>
                      <span class="comment">// that parentState was in the last time parentState was exited, or the history state's default</span>
                      <span class="comment">// state if parentState has never been entered.</span>
                      <span class="name">signal</span>: <span class="name">button</span>.<span class="name">clicked</span>
                  }
              }
          }
      }
  }

</pre>
<br style="clear: both" /><p>默认情况下，历史状态是浅的，这意味着它不会记住嵌套的状态。这可以通过<a href="qml-qtqml-statemachine-historystate.html#historyType-prop">historyType</a>属性配置。</p>
<p><b>参见</b><a href="qml-qtqml-statemachine-statemachine.html">StateMachine</a> 和 <a href="qml-qtqml-statemachine-state.html">State</a>。</p>
<!-- @@@HistoryState -->
<h2>属性文档</h2>
<!-- $$$defaultState -->
<div class="qmlitem"><div class="qmlproto">
<div class="table"><table class="qmlname">
<tr valign="top" class="odd" id="defaultState-prop">
<td class="tblQmlPropNode"><p>
<a name="defaultState-prop"></a><span class="name">defaultState</span> : <span class="type"><a href="qml-qtqml-statemachine-qabstractstate.html">QAbstractState</a></span></p></td></tr>
</table></div>
</div><div class="qmldoc"><p>此历史状态的默认状态。</p>
<p>默认状态指示要转换到的状态(如果以前从未输入父状态)。</p>
</div></div><!-- @@@defaultState -->
<br/>
<!-- $$$historyType -->
<div class="qmlitem"><div class="qmlproto">
<div class="table"><table class="qmlname">
<tr valign="top" class="odd" id="historyType-prop">
<td class="tblQmlPropNode"><p>
<a name="historyType-prop"></a><span class="name">historyType</span> : <span class="type"><a href="qml-enumeration.html">enumeration</a></span></p></td></tr>
</table></div>
</div><div class="qmldoc"><p>此历史状态记录的历史类型。</p>
<p>该属性的默认值是<a href="qml-qtqml-statemachine-historystate.html">HistoryState</a>.ShallowHistory。</p>
<p>此枚举指定<a href="qml-qtqml-statemachine-historystate.html">HistoryState</a>记录的历史类型。</p>
<ul>
<li><a href="qml-qtqml-statemachine-historystate.html">HistoryState</a>.ShallowHistory 只记录父状态的直接子状态。在本例中，以history状态为目标的转换将以父状态上次退出时的直接子状态结束。这是默认值。</li>
<li><a href="qml-qtqml-statemachine-historystate.html">HistoryState</a>.DeepHistory 将记录嵌套状态。在这种情况下，以历史状态为目标的转换将最终处于父类上次退出时所在的嵌套最深的后代状态。</li>
</ul>
</div></div><!-- @@@historyType -->
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